Fecal incontinence refers to the involuntary loss of gas or liquid stool (minor incontinence) or the involuntary loss of solid stool (major incontinence). Surveys indicate that fecal incontinence affects between 2 and 7 percent of the general population, although the true incidence may be much higher since many people are hesitant to discuss the problem with a healthcare provider.
Minor fecal incontinence affects men and women equally, but women are almost twice as likely as men to report major incontinence. Fecal incontinence is also more common in older adults. It is particularly common in nursing home residents, with studies suggesting that almost half of all residents are incontinent. Fecal incontinence can undermine self-confidence, create anxiety, and lead to social isolation; however, fecal incontinence is a treatable condition. Treatment can lessen symptoms in most cases and can often completely cure incontinence.
Continence requires the normal function of both the lower digestive tract and the nervous system. The anal sphincters, along with the pelvic muscles that surround the end of the digestive tract, ensure controlled movement of digestive tract contents. There are many possible causes of fecal incontinence. In most cases, incontinence results from some combination of these causes.
Three types of treatment are commonly used for fecal incontinence: medical therapy, biofeedback, and surgery. Medical therapy includes medication and certain measures that can reduce the frequency of incontinence and firm up the stools, which can reduce or eliminate episodes of fecal leakage. Often, basic measures will improve minor incontinence, but more aggressive measures may be needed to control frequent or severe episodes of leakage. Bulking substances that promote bulkier stools may help control diarrhea by thickening the stools. Methylcellulose (a form of fiber) is one type of bulking substance that is commonly used. Increasing dietary fiber may also help to bulk stools. Anti-diarrheal medications such as loperamide and diphenoxylate reduce the frequency of stools and are helpful in treating fecal incontinence. Loperamide can also increase the tone (tightness) of the anal sphincter muscle. When taken before meals, anticholinergic medications (such as the prescription drug hyoscyamine), by reducing contractions in the colon, can decrease the incontinence that occurs after meals in some people.
Biofeedback is a safe and noninvasive way of retraining muscles. During biofeedback training, sensors are used to help the patient identify and contract the anal sphincter muscles which help maintain continence. This is usually done in a healthcare provider or physical therapist's office. Biofeedback can be successful, although results can be variable. The people most likely to benefit from this type of therapy are those who can contract the anal sphincter muscle and have some sensation when they need to have a bowel movement. The effects of biofeedback may begin to decline six months after the initial training and retraining may be helpful.
Sacral nerve electrical stimulation can eliminate leakage in 40 to 75 percent of people whose anal sphincter muscles are intact. An electrode is surgically inserted near a nerve in the sacrum (low back). It is not entirely clear how sacral nerve stimulation works. The treatment is invasive, requiring surgical implantation. Some patients develop complications from the surgery, including pain, device malfunction, or infection, which may require that the device be removed or replaced. At present, this treatment is generally reserved for people with an intact or repaired anal sphincter who have not shown improvement with other treatments.
Electrical stimulation of the anal sphincter involves using a mild electrical current to stimulate the anal sphincter muscles to contract, which can strengthen the muscles over time. The electrical current is applied using a small probe, which the patient inserts inside the rectum for a few minutes every day for 8 to 12 weeks. A controlled trial suggested that electrical stimulation is only a modest benefit, possibly from increasing sensation in the anal area; this treatment, however, is inexpensive, non-invasive, and has few to no side effects. It may, however, be uncomfortable for patients who understandably may not like frequently inserting the stimulator device.
Several different surgical procedures can help alleviate fecal incontinence. Surgical repair can reduce or resolve incontinence, particularly for women who develop a tear in the external anal sphincter during childbirth and in people with injury of the sphincter due to surgery or other causes. Surgery cures fecal incontinence in 80 percent of women with childbirth-related sphincter tears.
In people who have irreparable damage of the sphincters, muscles can be transferred from other areas of the body, usually the leg or buttock, and surgically placed around the anal canal. These muscles mimic the action of the damaged sphincters. Muscle transfer surgery can restore continence in up to 73 percent of people with otherwise irreparable damage. An alternative to a transferred muscle is a synthetic anal cuff that can be inflated to hold back feces and deflated to allow bowel movements. However, this type of procedure is only performed in specialized centers. Complications can occur even when these surgeries are performed by experts.
Colostomy is a surgical procedure in which the colon is surgically attached to the abdominal wall. Stool is collected in a bag that fits snugly against the skin. This eliminates leakage of stool from the rectum. Variations on the procedure may allow the person to control bowel emptying. Colostomy is usually a last resort, after other treatments have failed. It may also be considered for people with intolerable symptoms who are not candidates for any other therapy.
Prior art systems and methods for electrical stimulation address the anal sphincter, on a collective basis, and do not distinguish between internal and external anal sphincter stimulation, which can produce quite different physiological results. The internal anal sphincter is a smooth muscle which is tonically contracted, is not under voluntary control, and is innervated by the submucosal nerve plexus. The internal anal sphincter maintains the tone of the sphincter and is resistant to fatigue. On the other hand, the external anal sphincter is a skeletal muscle which is not tonically contracted, is under voluntary control, and is innervated by the sacral and pudendal nerves, providing the voluntary control to the sphincter muscle, which is extremely susceptible to fatigue. Resting pressure is provided mostly by the internal anal sphincter, whereas squeezing pressure is provided by the external sphincter.
It would therefore be advantageous to stimulate the two sphincters differentially with different stimulation algorithms or different lead configurations due to their distinct physiology and function to prevent fatigue and improve tolerance. Since sphincter control relies on multiple mechanisms, specifically with respect to energy efficiency, tolerance, and fatigue issues, it is advantageous to stimulate multiple structures with different stimulation algorithms. In order to electrically stimulate two anatomical structures, prior art systems and methods would require at least two pairs of stimulation electrodes (that is, at least two microdevices or at least four leads). Due to anatomical limitations, it may be difficult to accommodate or precisely place multiple leads into the anal sphincter. It would, however, be advantageous to put one electrode in each individual structure, thereby using less leads and/or microdevices to achieve the desired stimulation scenario.
Accordingly, there is a need for a safe and effective method of treatment that can help alleviate symptoms of anal incontinence in the long term, without the need for invasive surgery. In addition, there is not only a need for improved devices in electrical stimulation based therapies for anal incontinence, but there is also a need for a safe and minimally invasive method and system that enables easy and expeditious deployment of such devices at any desired location in the body. Most of the currently available devices are available for surgical or laparoscopic implantation and suffer from common problems of pocket infection, lead dislodgment, or fracture. Furthermore, there is also a need for a device and method for implanting microdevices within the rectum or the anal canal.